Gastrointestinal (GI) motility is a coordinated neuromuscular process that transports nutrients through the digestive system. C. Scarpignato, Dig. Dis. 15: 112 (1997). Impaired GI motility, which may be involved in gastroesophageal reflux disease, gastroparesis (e.g., diabetic and postsurgical), irritable bowel syndrome and constipation, is one of the largest health care burdens of industralized nations. S. D. Feighner et al., Science 284: 2184-2188 (Jun. 25, 1999). Impaired GI motility can also lead to emesis (e.g., that caused by cancer chemotherapy agents), postoperative ileus and colonic pseudo-obstruction.
Very few compounds are known in the art to be useful for treating impaired GI motility. For example, PROPULSID® which contains cisapride monohydrate is an oral gastrointestinal agent (see U.S. Pat. No. 4,962,115). It is indicated for the symptomatic treatment of adult patients with nocturnal heartburn due to gastroesophageal reflux disease. Other prokinetic agents include, for example, metoclopramide, erythromycin, domperidone, ondansetron, tropisetron, mosapride and itopride. However, these therapeutic regimens suffer from numerous problems. For instance, PROPULSID® was recently removed from the market due to its potential to induce cardiac arrhythmias. A more effective, physiological way to stimulate GI motility would be highly desirable.
Growth hormone, which is secreted from the pituitary, stimulates growth of all tissues of the body that are capable of growing. In addition, growth hormone is known to have the following basic effects on the metabolic processes of the body: (1) increased rate of protein synthesis in all cells of the body; (2) decreased rate of carbohydrate utilization in cells of the body; and (3) increased mobilization of free fatty acids and use of fatty acids for energy. As is known to those skilled in the art, the known and potential uses of growth hormone are varied and multitudinous. See “Human Growth Hormone,” Strobel and Thomas, Pharmacological Reviews, 46, pg. 1-34 (1994). Also, these varied uses of growth hormone are summarized in International Patent Application, Publication Number WO 97/24369.
Various ways are known to release growth hormone (see Recent Progress in Hormone Research, vol. 52, pp. 215-245 (1997); and Front Horm Res. Basel, Karger, vol. 24, pp. 152-175 (1999)). For example, chemicals such as arginine, L-3,4-dihydroxyphenylalanine (L-DOPA), glucagon, vasopressin, and insulin induced hypoglycemia, as well as activities such as sleep and exercise, indirectly cause growth hormone to be released from the pituitary by acting in some fashion on the hypothalamus perhaps either to decrease somatostatin secretion or to increase secretion of growth hormone releasing factor (GRF) or ghrelin (see Nature, vol. 402, pp. 656-660 (Dec. 9, 1999)), or all of these.
In cases where increased levels of growth hormone were desired, the problem was generally solved by providing exogenous growth hormone or by administering GRF, IGF-1 or a peptidyl compound which stimulated growth hormone production and/or release. In any case, the peptidyl nature of the compound necessitated that it be administered by injection. Initially, the source of growth hormone was the extraction of the pituitary glands of cadavers. This resulted in a very expensive product and carried with it the risk that a disease associated with the source of the pituitary gland could be transmitted to the recipient of the growth hormone. Recombinant growth hormone has become available which, while no longer carrying any risk of disease transmission, is still a very expensive product which must be given by injection. In addition, administration of exogenous growth hormone may result in side-effects, including edema, and does not correlate with the pulsatile release seen in the endogenous release of growth hormone.
Certain compounds have been developed which stimulate the release of endogenous growth hormone. Peptides which are known to stimulate the release of endogenous growth hormone include growth hormone releasing hormone and its analogs, the growth hormone releasing peptides, GHRP-6 and GHRP-1 (described in U.S. Pat. No. 4,411,890; International Patent Application, Publication No. WO 89/07110; and International Patent Application, Publication No. WO 89/07111), and GHRP-2 (described in International Patent Application, Publication No. WO 93/04081), as well as hexarelin (J. Endocrinol. Invest., 15 (Suppl. 4): 45 (1992)). Other compounds possessing growth hormone secretagogue activity are disclosed in the following International Patent Applications (listed by Publication Nos.), issued U.S. Patents and published European Patent Applications: WO 98/46569, WO 98/51687, WO 98/58947, WO 98/58949, WO 98/58950, WO 99/08697, WO 99/09991, WO 95/13069, U.S. Pat. Nos. 5,492,916, 5,494,919, WO 95/14666, WO 94/19367, WO 94/13696, WO 94/11012, U.S. Pat. No. 5,726,319, WO 95/11029, WO 95/17422, WO 95/17423, WO 95/34311, WO 96/02530, WO 96/22996, WO 96/22997, WO 96/24580, WO 96/24587, U.S. Pat. No. 5,559,128, WO 96/32943, WO 96/33189, WO 96/15148, WO 96/38471, WO 96/35713, WO 97/00894, WO 97/07117, WO 97/06803, WO 97/11697, WO 97/15573, WO 97/22367, WO 97/23508, WO 97/22620, WO 97/22004, WO 97/21730, WO 97/24369, U.S. Pat. No. 5,663,171, WO 97/34604, WO 97/36873, WO 97/40071, WO 97/40023, WO 97/41878, WO 97/41879, WO 97/46252, WO 97/44042, WO 97/38709, WO 98/03473, WO 97/43278, U.S. Pat. Nos. 5,721,251, 5,721,250, WO 98/10653, U.S. Pat. Nos. 5,919,777, 5,830,433 and EP 0995748.
In addition, the following growth hormone secretagogues are known in the art: MK-0677, L-162752 and L-163022 (Merck); NN703 and ipamorelin (Novo Nordisk); hexarelin (Pharmacia & Upjohn); GPA-748 (KP102, GHRP-2) (American Home Products); and LY444711 (Eli Lilly). The following agents that stimulate GH release via GHRH/GRF receptor (including GHRH/GRF derivatives, analogs and mimetics) are known in the art: Geref (Ares/Serono); GHRH (1-44) (BioNebraska); Somatorelin (GRF 1-44) (Fujisawa/ICN); and ThGRF (Theratechnologies).
Endocrine Reviews 18(5): 621-645 (1997) provides an overview of peptidomimetic regulation of growth hormone secretion by growth hormone secretagogues. Horm. Res. 1999; 51 (suppl 3):16-20 (1999), examines the clinical and experimental effects of growth hormone secretagogues on various organ systems. Drug Discovery Today, Vol. 4, No. 11, November 1999; and TEM Vol. 10, No. 1, 1999, disclose potential therapeutic applications of growth hormone secretagogues, including their use in treating growth hormone disorders such as growth hormone deficiency (GHD), age-related conditions, obesity and catabolic conditions, and their use in sleep enhancement.
International Patent Applications, Publication Nos. WO 97/24369 and WO 98/58947 disclose that certain growth hormone secretagogues are useful for the treatment or prevention of osteoporosis, congestive heart failure, frailty associated with aging, obesity; accelerating bone fracture repair, attenuating protein catabolic response after a major operation, reducing cachexia and protein loss due to chronic illness, accelerating wound healing or accelerating the recovery of burn patients or patients having undergone major surgery; improving muscle strength, mobility, maintenance of skin thickness, metabolic homeostasis or renal homeostasis. Published European patent application 0995748 discloses that certain dipeptide growth hormone secretagogues are useful for the treatment or prevention of musculoskeletal frailty, including osteoporosis.
The administration of a growth hormone secretagogue is also known to enhance the quality of sleep, which is disclosed in International Patent Application, Publication No. WO 97/24369. A growth hormone secretagogue can be administered to a patient having or at risk of having one or more of the conditions or symptoms recited above. Commonly assigned U.S. nonprovisional patent application Ser. No. 09/290985, filed Apr. 13, 1999, discloses pharmaceutical compositions comprising certain β3 adrenergic agonists and growth hormone secretagogues or growth hormone, and their use for treating diabetes, obesity, hyperglycemia, frailty associated with obesity or frailty associated with aging, and for enhancing the quality of sleep in a mammal. International Patent Application, Publication No. WO 98/58949, discloses the treatment of insulin resistance with certain growth hormone secretagogues.
Abstract OR4-5 from The Endocrine Society 81st Annual Meeting (12-15 June 1999), San Diego, Calif., discloses that growth hormone (GH) therapy resulted in marked clinical improvement in patients with active Crohn's disease (regional inflammation of the intestines).
S. D. Feighner et al., Science 284: 2184-2188 (Jun. 25, 1999), discloses that a heterotrimeric guanosine triphosphate-binding protein (G protein)-coupled receptor for motilin (a 22-amino acid peptide hormone expressed throughout the gastrointestinal tract of humans and other species) was isolated from the human stomach, and that its amino acid sequence was found to be 52 percent identical to the human receptor for growth hormone secretagogues.